Current theories of quality coding in gustation are based largely upon single neuron data collected in peripheral nerves and the lower brain stem of anesthetized rodents. Thalamic and cortical gustatory areas have been neglected because neurons in these areas are very sensitive to general anesthesia and the technology for chronic recording in rodents is inadequate. The research proposed will circumvent these obstacles by using established techniques for chronic electrophysiological recording in awake, behaving primates. This research represents a logical extension of four primate neuroanatomical experiments completed in this laboratory. These experiments have described the organization of gustatory and visceral afferent systems from the medulla to the cortex. Three forebrain areas that receive gustatory afferent projections will be investigated: the thalamic taste area, insular-opercular cortex, and a small cortical area on the lateral convexity that receives an overlapping projection from the thalamic oral somatosensory relay. Intraoral fluid stimuli will be used to determine: 1) the degree of gustatory, tactile, and thermal specificity of individual neurons in each area; 2) the differential sensitivity of individual neurons to various sapid stimuli; and 3) the ability of individual neurons to respond selectively to complex, behaviorally relevant stimuli. Additional experiments with lightly anesthetized primates, will determine if gustatory cortex is topographically organized and, if so, whether its basis is spatial, chemical or related to specific subpopulations of receptors. These data, in addition to describing normal taste perception, may be relevant to certain pathological types of ingestive behavior (e.g. anorexia nervosa and bulimia) that require cortical involvement.